Improving GNSS Meteorology by Fusing Measurements of Several Co-located Receivers on the Observation Level

Zenith Wet Delay (ZWD) estimation is a key component for the Global Navigation Satellite System (GNSS) meteorology. At present, the Zenith Hydrostatic Delay (ZHD) can be computed with sufficient accuracy by means of empirical models, while the ZWD, which is induced by water vapor with the nature of highly spatio-temporal variability, is typically estimated as an unknown parameter in Precise Point Positioning (PPP). Due to GNSS receiver noise and the system biases of GNSS receivers, the accuracy as well as the precision of ZWD estimates is limited. In this study, we propose a novel fusion model based on undifferenced GNSS pseudorange and carrier-phase observations for sites, which have several receivers connected to a single antenna or which are separated horizontally by only a few meters. By fusing GNSS measurements collected by multiple receivers on the observation level, our model can provide common ZWD estimates with a high temporal resolution which can then be used for more accurate and reliable meteorologic applications on a local scale. According to results with simulated and real data, it is revealed that such combined ZWD estimates are superior to single receiver estimates in terms of precision and accuracy. On the other hand, it is confirmed that the estimation of a common ZWD parameter leads to an improvement in positioning accuracy and precision, especially in the vertical component.